Removing Hard Cement Pointing Without Damaging the Brick

Why the old pointing has to come out

Where a soft brick or stone stack has been pointed in hard cement, leaving it in place and pointing over the top does not work. The strong mortar is the reason the masonry is failing, and a new lime joint laid beside or over it would be shielded from the very movement it is meant to take up.

The cement ribbon is usually standing proud of an eroded brick face, so it can look as though removal ought to be easy. In practice it is the hardest part of the job. The cement is stronger than the brick it is touching, it has often bonded to the edges, and every blow that dislodges it can also lift the arris of the brick, which is the sharp corner that gives a stack its crisp, finished look.

The aim is to take the joint out cleanly, and to leave the brick as it was found, or only slightly the worse for its previous treatment. That takes patience, and it is the reason the process cannot be hurried or treated as a quick tidy-up.

Tools and the hand approach

On hard, modern brick, a mortar raking tool or a grinder with a guard may be acceptable. On the soft handmade brick and sandstone common around chimney repairs in Neston, an angle grinder tends to overcut, burn into the brick edge and leave a scar that cannot be pointed out. Wide discs also cut beyond the joint at the corners, where horizontal and vertical joints meet.

The usual approach is slow and manual. A fine plugging chisel or a narrow raking tool is placed in the joint and tapped lightly, first to break the bond at the brick edge and then to loosen the cement in short pieces. Working from the middle of the joint outwards, rather than levering against the brick, keeps pressure off the arris. Vertical joints are done first, then horizontal, and the stack is brushed down as the work goes so that you can see what is happening.

Where the cement is exceptionally stubborn, a very small powered tool may be used with a narrow blade, under close control, but never as the main method. If a brick begins to break, the work stops and the approach changes. Details of mortar choice for the repointing that follows are in Repointing a Chimney: Why the Mortar Mix Matters More Than the Finish.

How deep is deep enough

A rule of thumb is that the raking depth should be about twice the joint width, with a minimum that gives the new mortar enough bite to hold. A thin joint needs less depth than a wide one. The joint should be taken back until sound material is reached, which is often deeper than the surface appearance suggests, since cement tends to sit in a plug behind a thin outer skin.

The back of the raked joint should be square and clean, not rounded, and free of dust. A joint that is deeper in some places and shallower in others will cure unevenly and weather unevenly, so the depth is checked as the work proceeds. Where a joint is very deep, the new mortar is put in more than one pass, letting each layer firm up before the next.

If bricks themselves are badly decayed behind the cement, the extent becomes clear only once the joint is open. Some stacks reveal that more than pointing is needed, and the choice of repointing, partial rebuild or removal is then discussed, as in Repoint, Rebuild or Remove? How the Decision Gets Made.

Protecting the roof and the people below

Raking out sends fine dust and fragments down, and the covering beneath the stack is easily marked. Old clay tiles and thin natural slates are brittle, so the roof around the stack is protected with boards and sheeting, and debris is collected as it falls and lowered, never dropped. Gutters are covered or cleared before and after.

The ground below is kept clear while the work is done, and neighbours are told what is happening. Dust from old mortar is cleared as it is made, and it is never swept into a gutter or a downpipe, where it will set into a blockage.

Because the working platform is a scaffold with proper boarding, the person raking out has both hands free and a firm footing, which is what makes careful hand work possible in the first place. It also means the work can be paused safely if a brick is found to be weaker than expected, and the next step agreed with you before anything else is touched.

What rushing risks and how the job is judged

A rushed rake-out leaves joints that are too wide, bricks with chipped corners, and cement still stuck in the bed. The new pointing then has little to hold on to, or must be proud of the face to cover the damage. Either way the stack looks worse than before, and the weathering that follows is quicker.

There are a few simple ways to judge the result. The brick edges should be intact, with the same sharpness as the undamaged areas. The joints should be a consistent depth with square backs. No grey cement should remain in the corners, and the dust should be cleared before any mortar goes in. On a finished stack, the new joint should sit slightly back from the face and shed water across the brick.

This work is done from a safe working platform, not from a ladder, and we do the outside of stacks only. Flue and appliance matters belong to a HETAS or Gas Safe registered installer or a sweep. Ask for a free written quotation that states how the old pointing will be removed and to what depth.